1. Technical Field of the Invention
This invention relates generally to communication systems and more particularly to wireless communication systems.
2. Description of Related Art
Communication systems are known to support wireless and wire lined communications between wireless and/or wire lined communication devices. Such communication systems range from national and/or international cellular telephone systems to the Internet to point-to-point in-home wireless networks. Each type of communication system is constructed, and hence operates, in accordance with one or more communication standards. For instance, wireless communication systems may operate in accordance with one or more standards including, but not limited to, IEEE 802.11, Bluetooth, advanced mobile phone services (AMPS), digital AMPS, global system for mobile communications (GSM), code division multiple access (CDMA), local multi-point distribution systems (LMDS), multi-channel-multi-point distribution systems (MMDS), and/or variations thereof.
Depending on the type of wireless communication system, a wireless communication device, such as a cellular telephone, two-way radio, personal digital assistant (PDA), personal computer (PC), laptop computer, home entertainment equipment, et cetera communicates directly or indirectly with other wireless communication devices. For direct communications (also known as point-to-point communications), the participating wireless communication devices tune their receivers and transmitters to the same channel or channels (e.g., one of the plurality of radio frequency (RF) carriers of the wireless communication system) and communicate over that channel(s). For indirect wireless communications, each wireless communication device communicates directly with an associated base station (e.g., for cellular services) and/or an associated access point (e.g., for an in-home or in-building wireless network) via an assigned channel. To complete a communication connection between the wireless communication devices, the associated base stations and/or associated access points communicate with each other directly, via a system controller, via the public switch telephone network, via the Internet, and/or via some other wide area network.
For each wireless communication device to participate in wireless communications, it includes a built-in radio transceiver (i.e., receiver and transmitter) or is coupled to an associated radio transceiver (e.g., a station for in-home and/or in-building wireless communication networks, RF modem, etc.). As is known, the transmitter includes a data modulation stage, one or more intermediate frequency stages, and a power amplifier. The data modulation stage converts raw data into baseband signals in accordance with a particular wireless communication standard. The one or more intermediate frequency stages mix the baseband signals with one or more local oscillations to produce RF signals. The power amplifier amplifies the RF signals prior to transmission via an antenna.
As is also known, the receiver is coupled to the antenna and includes a low noise amplifier, one or more intermediate frequency stages, a filtering stage, and a data recovery stage. The low noise amplifier receives inbound RF signals via the antenna and amplifies then. The one or more intermediate frequency stages mix the amplified RF signals with one or more local oscillations to convert the amplified RF signal into baseband signals or intermediate frequency (IF) signals. The filtering stage filters the baseband signals or the IF signals to attenuate unwanted out of band signals to produce filtered signals. The data recovery stage recovers raw data from the filtered signals in accordance with the particular wireless communication standard.
In wireless networks, such 802.11 networks, the wireless transceiver (e.g., the client station) is required to occasionally scan the available channels to see whether there are other nodes with which to communicate (i.e., other channels are supporting data of interest to the wireless communication device). Because of the nature of wireless networks, the scanning process requires that the station to temporarily leave the channel that is supporting a current communication by tuning and listening to one or more different channels to determine if there is any interest in association with one of these other channels. A significant period of time is required to make such a determination for each channel. In many wireless local area networks (WLAN), multiple frequencies and/or network interface protocols may be used (e.g., IEEE 802.11b, IEEE 802.11a, and/or IEEE 802.11g protocols), which increases the number of channels that must be scanned and correspondingly increases the time it takes to scan all of the channels.
While the time it takes to scan multiple channels over multiple network interface protocols, the data throughput performance impact on the station is modest. However, the data throughput for higher layer protocols, such as Transmission Control Protocol/Internet Protocol (TCP/IP) may be significantly impacted. Such a significant impact results because TCP/IP measures the time that expires from when a source sends a packet to a destination until the source receives an acknowledgement (ACK) from the destination that it received the packet. If the time is greater than expected (e.g., a few hundred milliseconds plus some tolerance that accounts for reasonable transmission time variations), TCP/IP may interpret this as congestion (i.e., the network infrastructure is overworked and is slow in transferring packets). When congestion is suspected, TCP/IP uses a multiplicative decrease congestion avoidance algorithm that dramatically reduces the transmission rate of packets from the source to the destination. When the congestion is reduced, TCP/IP uses a slow start algorithm that slowly increases the packet rate between the source and the destination.
Unfortunately, TCP/IP cannot determine between actual congestion of the network and when the station is scanning other channels and not supporting the TCP/IP packet transmissions. If the station is scanning other channels for a significant period of time (e.g., a few hundred milliseconds), TCP/IP may view this absence of support as congestion and evoke the multiplicative decrease congestion avoidance algorithm. As such, the TCP/IP throughput is unnecessarily reduced.
Therefore, a need exists for a method and apparatus for interoperability of a network interface protocol with an Internet interface protocol to ensure data high throughput of the higher layer Internet interface protocol.